Knife sharpener

ABSTRACT

The grinding wheel of a sharpener for an involute cutting blade is held on the blade cutting edge by tiltably mounting the grinding assembly relative to the knife cutting edge.

United States Patent [191 Good June 28, 1974 [5 1 KNIFE SHARPENER 2,735,247 2/1956 Holzhausen et a1. 51/168 x 2,933,865 4/1960 M'll 51/249 [75] Invent Paul 600d Luthemne, 2,978,848 4/1961 Ra ini 51/247 73 Assignee: Speedco Inc Baltimore Md 3,423,882 H1969 Tucker et al. 51/248 X [22] Filed: June 23, 1972 Primary Exammer-Othell M. S1mpson 1 p 265,439 7 Assistant Examiner-Nicholas P. Godici [52] 11.8. CI. 51/248, 83/1741 [51 Int. Cl B24b 3/46 ABSTRACT [58] held of Search f gi 1 ,2 The grinding wheel of a sharpener for an involute cut- 4 ting blade is held on the blade cutting edge by tiltably mounting the grinding assembly relative to the knife [56] References Clted cutting edge UNITED STATES PATENTS 2,665,531 l/l954 Silvertsen 51/248 9 Claims, 7 Drawing Figures mm muuza 1974 3.820.289

sum 3 OF 3 FIG.6

. 1 V KNIFE SHARPENER' This invention relates to a knife grinder for sharpening an involute knife.

Raine U.S. Pat. Number 2,978,848, discloses a grinder for sharpening an involute knife, and the disclosure of this patent is incorporated by reference into this application. In Raine the grinding wheel is positioned on the knife edge by means of a guide block, which rides on one of the bevelled knife edge surfaces. However, as a practical matter, because of the geometry of the vertical movement of the guide block, the grinding wheel only approximately follows a portion of the knife edge. The result is that the entire knife edge is not satisfactorily sharpened.

The object of this invention is to improve upon the grinding assembly geometry so that the knife edge is uniformly sharpened along its entire length. Other objects are to produce improved means for deburring the sharpened knife edge, and producing means so that the knife can be sharpened while it is being continuously turned in one direction.

In general, these objects are obtained by providing tiltable supporting means for the grinding assembly including the guiding block or roller. This permits the grinding wheel to remain in contact with the bevelled knife edge surface over the entire length of the knife edge. A back grinding wheel is positioned on the rear side of the knife to take off any burr produced by the grinding wheel. A dash-pot is used with the grinding assembly for checking the drop of the assembly when it passes over the gap in the involute knife edge. Novel adjustable spring means are used for holding the grinding wheel and the back grinding wheel in a firm contact with the knife edge.

The means by which the objects of this invention are obtained are described more fully with respect to the accompanying drawings, in which;

FIG. I is a front view of the prior art knife sharpener as taken from FIG. of the aforesaid Raine patent;

FIG. 2 is a schematic of the geometry of the grinder assembly movement in the Raine apparatus;

FIG. 3 is a side view of the instant invention;

FIG. 4 is a front view of the instant invention;

FIG. 5 is a cross-sectional view of the mounting for the main grinding wheel;

FIG. 6 is a cross-sectional view of the mounting for the back grinding wheel; and

FIG. 7 is a view partially in section of a modification of a portion of FIG. 6.

As shown in FIG. 1, in Raine, the rear knife guard 11 mounted on the cutting machine has extending therethrough a shaft 12 upon which is mounted the involute knife 13 having a knife edge 14. The grinding assembly is only vertically movable on guide rail 22. This assembly includes a guide block 36, a back deburring grinding wheel 52 and a main grinding wheel 62. The guide block rides on the secondary bevel of the knife edge 14.

The radius, or the distance between the center of the shaft 12 and the cutting edge 14, changes in an involute. Because the Raine apparatus only provides for, and is restricted to, vertical movement of the grinding assembly by reason of guide rail 22, this causes an incomplete grinding as shown in the schematic of FIG. 2. Lines A and B represent the vertical movement of the guide block 36 and the grinding wheel 62, respectively.

If, at the least radius, the guide block 36 contacts the bevel at the cutting edge 14 at point C and the grinding wheel 62 makes contact with edge 14 at point D, it is seen that if these points travel vertically upwardly in a straight line, when the guide block contact point C reaches the larger knife radius at point P, the grinding wheel contact point D will have been raised to point E and will be considerably above and out of contact with the involute edge of the knife. Therefore, the grinding wheel will gradually move further and further away from the cutting edge 14 as the grind assembly rises.

In this invention, to correct this difficulty, the grinding point is moved downwardly from point E to meet the cutting edge 14 at point G. This is done by providing means for tilting the grinding wheel support at an angle X.

As shown in FIGS. 3 and 4, in this invention the invo lute cutting knife 70 is mounted on a shaft 72. The knife has a cutting edge 74. The grinder assembly includes the front main grinding wheel 76, the back grinding or deburring wheel 78 and the guiding means which may be a of guide roller 80 coaxial with the back grinding wheel and which rides on the secondary bevel of the knife edge. This assembly is mounted on an arm 82. This is composed of a flat bar 83 having its upper end joined to the grinder assembly and a yoke at its lower end to which are bolted finger 85. The yoke finger tiltably engage the shaft 72 and permit relative adjustment with arm 82. Pivotally joined to the rear knife guard 86 is an arm 88, which has its other end pivoted to the grinder assembly for permitting angular movement of the grinder assembly as it is moved vertically by the guide roller 82 riding on the knife edge bevel. While element 88 is recited as an arm, it is to be noticed that the function of this arm is merely to hold the grinder assembly in proper position with respect to the plane of the knife as it moves away from the axis of the knife during the grinding operation. The pivot 88a on which the grinder assembly is mounted may move in an arc as it will if it is controlled by arm 88 as shown, but the tilt of the grinding assembly with respect to a radius through the axis of the knife will be the same at the same distance from the axis of shaft 72 regardless of the circumferential position of the grinding assembly so, while the grinding assembly follows, under the influence of the illustrated arm 88, an arc lying generally radially of the shaft 72, it is at once seen that any guide means that supports the grinding assembly in its position with respect to the plane of the knife as it moves inwardly and outwardly as it follows the curve of the knife is not dependent on the path of the pivot, but on the action of arm 82 and yoke 85. To this arm is attached a dash-pot 92 for checking the movement of the grinding assembly as it drops while passing over the large end 96 of the cutting knife. The yoke 84 then drops down to shaft 72. The knife is turned manually by a removable handle 98. The use of the dash-pot permits the knife edge to be continuously rotated clock- In order to compensate for variations in the cutting edge bevel, the main grinding wheel 76 is spring loaded, as shown in FIG. 5, by means of a spring 106 and an adjusting knob 107. In an analgous manner the back grinding wheel 78 is spring loaded by a spring Some knives have a curved back side on their nonbevelled sides, with a cutting edge plane 11 l, as shown in FIG. 7. In order to keep the back grinding wheel 78 into contact with the cutting edge, the wheel 78 is mounted on its shaft by means of a resilient bushing 112 so that the wheel can tilt and stay in contact with the cutting edge. The pressure on the wheel can be changed by adding or removing one or more shims 114.

Having now described the means by which the objects of the invention are obtained, I claim:

1. An apparatus for sharpening the cutting edge of a rotary involute knife blade mounted on a shaft, a grinding assembly including a grinding wheel mounted at an angle to the plane of the involute knife to be sharpened, and guide means contacting said blade adjacent said cutting edge to position said grinding wheel with respect to said cutting edge, a guide arm, said grinding assembly being mounted on said guide arm at one end thereof, the other end of said guide arm being bifurcated and straddling said shaft so that said guide arm extends generally radially from said shaft, and an arm pivotally connected at one end adjacent said grinding assembly, and at the other end pivotally connected to a support in fixed position with respect to said shaft, the axes of said pivots being parallel to said shaft.

2. The apparatus of Claim 1 in which said bifurcated end is angularly adjustable with respect to said guide arm in a plane parallel to the plane of the knife to be sharpened.

3. The apparatus of Claim 1 including dash-pot s 4 means whereby sudden movement of the grinding wheel assembly will be avoided.

4. In an apparatus as in claim 1, further comprising adjustable spring means for holding said wheel in firm contact with the knife edge.

5. In an apparatus as in claim 1, further comprising an adjustable spring loaded back wheel joined to said assembly.

6. In an apparatus as in claim 5, said guiding means including a roller coaxial with said back grinding wheel.

7. In an apparatus for sharpening the cutting edge of a rotary involute knife mounted on a shaft of the type in which a grinder assembly is provided to move outwardly along the knife edge as the knife is rotated, radially movable guiding means including a pivot having an axis normal to the plane of said knife to pivotally support said grinder assembly in the plane of the knife while the grinder assembly is moved outwardly, means to control the tilt of said grinder assembly on said pivot including an arm extending from said grinder assembly generally radially toward said shaft, and means guided by said shaft to adjust the angle of said arm with respect to the radius of said shaft which radius includes said pivot as the grinder assembly moves toward or away from said shaft.

8. The knife sharpening apparatus of claim 7 in which said means to adjust the tilt of said grinder assembly on said pivot is a bifurcated element to straddle the said shaft.

9. The knife sharpening apparatus of claim 8 in which said bifurcated element is angularly adjustable with respect to said arm in a plane parallel to the plane of said knife. 

1. An apparatus for sharpening the cutting edge of a rotary involute knife blade mounted on a shaft, a grinding assembly including a grinding wheel mounted at an angle to the plane of the involute knife to be sharpened, and guide means contacting said blade adjacent said cutting edge to position said grinding wheel with respect to said cutting edge, a guide arm, said grinding assembly being mounted on said guide arm at one end thereof, the other end of said guide arm being bifurcated and straddling said shaft so that said guide arm extends generally radially from said shaft, and an arm pivotally connected at one end adjacent said grinding assembly, and at the other end pivotally connected to a support in fixed position with respect to said shaft, the axes of said pivots being parallel to said shaft.
 2. The apparatus of Claim 1 in which said bifurcated end is angularly adjustable with respect to said guide arm in a plane parallel to the plane of the knife to be sharpened.
 3. The apparatus of Claim 1 including dash-pot means whereby sudden movement of the grinding wheel assembly will be avoided.
 4. In an apparatus as in claim 1, further comprising adjustable spring means for holding said wheel in firm contact with the knife edge.
 5. In an apparatus as in claim 1, further comprising an adjustable spring loaded back wheel joined to said assembly.
 6. In an apparatus as in claim 5, said guiding means including a roller coaxial with said back grinding wheel.
 7. In an apparatus for sharpening the cutting edge of a rotary involute knife mounted on a shaft of the type in which a grinder assembly is provided to move outwardly along the knife edge as the knife is rotated, radially movable guiding means including a pivot having an axis normal to the plane of said knife to pivotally support said grinder assembly in the plane of the knife while the grinder assembly is moved outwardly, means to control the tilt of said grinder assembly on said pivot including an arm extending from said grinder assembly generally radially toward said shaft, and means guided by said shaft to adjust the angle of said arm with respect to the radius of said shaft which radius includes said pivot as the grinder assembly moves toward or away from said shaft.
 8. The knife sharpening apparatus of claim 7 in which said means to adjust the tilt of said grinder assembly on said pivot is a bifurcated element to straddle the said shaft.
 9. The knife sharpening apparatus of claim 8 in which said bifurcated element is angularly adjustable with respect to said arm in a plane parallel to the plane of said knife. 